1. Field of the Invention.
This invention principally relates to work-holding apparatus and, more particularly, to apparatus for holding a workpiece having an internal bore so that the surface of the bore can be honed or otherwise machined.
2. Description of the Related Art.
Conventional lathe chucks are not well adapted for holding a thin-walled object such as a cylindrical shell having an internal bore which requires honing, polishing, or various types of machining. The jaws of a conventional lathe chuck apply force to just a few points of the workpiece, thus tending to deform the shell. Sometimes such workpieces are held by hand or with a hand tool in order to perform honing operations on the interior surface of a bore in the workpiece. The lack of stability and the development of operator fatigue in such an approach are obvious, and the chance of marring the surface being worked on or of otherwise producing an unsatisfactory result clearly exists. In addition, holding a workpiece by hand against rotating machinery is an inherently risky procedure from the standpoint of operator safety.
It would be a great boon in machine shop practice if there existed a means for holding a workpiece for honing or otherwise machining the inside of a bore in the object without damaging the outer surface of the object, while providing sufficient holding strength and stability. Such a work-holding apparatus would be even more valuable if it were convenient to use, easy to install in a working position, economical to manufacture, and simple to service. It would also be advantageous if such a work-holding means had the capability of gripping a deformable object over its entire outer circumference without distorting its shape because of contact forces concentrated at just a few points.
Examples of improved devices which may be used for holding a workpiece and which are particularly adapted for holding a thin-walled, hollow, deformable workpiece without scratching or distorting its shape may be found in my prior U.S. Pat. Nos. 4,872,654 and 4,872,655. My present invention follows the same principle of establishing and maintaining a grip on the outer surface of a cylindrical workpiece but provides a more sophisticated and effective mechanism for applying the principle. In particular, the embodiments of the present invention achieve a greater degree of adjustability to the size of the workpiece in a given implement than is possible with respect to the devices of my prior patents.